.TH LDAP_OPEN 3 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" $OpenLDAP$
.\" Copyright 1998-2022 The OpenLDAP Foundation All Rights Reserved.
.\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
.SH NAME
ldap_init, ldap_initialize, ldap_open \- Initialize the LDAP library and open a connection to an LDAP server
.SH LIBRARY
OpenLDAP LDAP (libldap, \-lldap)
.SH SYNOPSIS
.nf
.ft B
#include <ldap.h>
.LP
.ft B
LDAP *ldap_open(host, port)
.ft
char *host;
int port;
.LP
.ft B
LDAP *ldap_init(host, port)
.ft
char *host;
int port;
.LP
.ft B
int ldap_initialize(ldp, uri)
.ft
LDAP **ldp;
char *uri;
.LP
.ft B
int ldap_connect(ldp)
.ft
LDAP *ldp;
.LP
.ft B
int ldap_set_urllist_proc(ld, proc, params)
.ft
LDAP *ld;
LDAP_URLLIST_PROC *proc;
void *params;
.LP
.ft B
int (LDAP_URLLIST_PROC)(ld, urllist, url, params);
.ft
LDAP *ld;
LDAPURLDesc **urllist;
LDAPURLDesc **url;
void *params;
.LP
.ft B
#include <openldap.h>
.LP
.ft B
int ldap_init_fd(fd, proto, uri, ldp)
.ft
ber_socket_t fd;
int proto;
char *uri;
LDAP **ldp;
.SH DESCRIPTION
.LP
.B ldap_open()
opens a connection to an LDAP server and allocates an LDAP
structure which is used to identify
the connection and to maintain per-connection information.
.B ldap_init()
allocates an LDAP structure but does not open an initial connection.
.B ldap_initialize()
allocates an LDAP structure but does not open an initial connection.
.B ldap_init_fd()
allocates an LDAP structure using an existing connection on the
provided socket.
One
of these routines must be called before any operations are attempted.
.LP
.B ldap_open()
takes \fIhost\fP, the hostname on which the LDAP server is
running, and \fIport\fP, the port number to which to connect.  If the default
IANA-assigned port of 389 is desired, LDAP_PORT should be specified for
\fIport\fP.  The \fIhost\fP parameter may contain a blank-separated list
of hosts to try to connect to, and each host may optionally by of the form
\fIhost:port\fP.  If present, the \fI:port\fP overrides the \fIport\fP
parameter to
.BR ldap_open() .
Upon successfully making a connection to an
LDAP server,
.B ldap_open()
returns a pointer to an opaque LDAP structure, which should be passed
to subsequent calls to
.BR ldap_bind() ,
.BR ldap_search() ,
etc. Certain fields in the LDAP structure can be set to indicate size limit,
time limit, and how aliases are handled during operations; read and write access 
to those fields must occur by calling
.BR ldap_get_option (3) 
and
.BR ldap_set_option (3)
respectively, whenever possible.
.LP
.B
ldap_init()
acts just like
.BR ldap_open() ,
but does not open a connection
to the LDAP server.  The actual connection open will occur when the
first operation is attempted.
.LP
.B ldap_initialize()
acts like
.BR ldap_init() ,
but it returns an integer indicating either success or the failure reason,
and it allows to specify details for the connection in the schema portion
of the URI.
The
.I uri
parameter may be a comma- or whitespace-separated list of URIs
containing only the
.IR schema ,
the
.IR host ,
and the
.I port
fields.
Apart from
.BR ldap ,
other (non-standard) recognized values of the
.I schema
field are
.B ldaps
(LDAP over TLS),
.B ldapi
(LDAP over IPC),
and
.B cldap
(connectionless LDAP).
If other fields are present, the behavior is undefined.
.LP
At this time,
.B ldap_open()
and 
.B ldap_init()
are deprecated in favor of
.BR ldap_initialize() ,
essentially because the latter allows to specify a schema in the URI
and it explicitly returns an error code.
.LP
.B ldap_connect()
causes a handle created by
.B ldap_initialize()
to connect to the server. This is useful in situations where a file
descriptor is required before a request is performed.
.LP
.B ldap_init_fd()
allows an LDAP structure to be initialized using an already-opened
connection. The
.I proto
parameter should be one of LDAP_PROTO_TCP, LDAP_PROTO_UDP,
or LDAP_PROTO_IPC
for a connection using TCP, UDP, or IPC, respectively. The value
LDAP_PROTO_EXT
may also be specified if user-supplied sockbuf handlers are going to
be used. Note that support for UDP is not implemented unless libldap
was built with LDAP_CONNECTIONLESS defined.
The
.I uri
parameter may optionally be provided for informational purposes.
.LP
.B ldap_set_urllist_proc()
allows to set a function
.I proc
of type
.I LDAP_URLLIST_PROC
that is called when a successful connection can be established.
This function receives the list of URIs parsed from the
.I uri
string originally passed to
.BR ldap_initialize() ,
and the one that successfully connected.
The function may manipulate the URI list; the typical use consists
in moving the successful URI to the head of the list,
so that subsequent attempts to connect to one of the URIs using the same LDAP handle
will try it first.
If
.I ld
is null,
.I proc
is set as a global parameter that is inherited by all handlers
within the process that are created after the call to
.BR ldap_set_urllist_proc() .
By default, no 
.I LDAP_URLLIST_PROC
is set.
In a multithreaded environment,
.B ldap_set_urllist_proc()
must be called before any concurrent operation using the LDAP handle is started.

Note: the first call into the LDAP library also initializes the global
options for the library. As such the first call should be single-threaded
or otherwise protected to insure that only one call is active. It is
recommended that
.BR ldap_get_option ()
or
.BR ldap_set_option ()
be used in the program's main thread before any additional threads are created.
See
.BR ldap_get_option (3).

.SH ERRORS
If an error occurs,
.B ldap_open()
and
.B ldap_init()
will return NULL and 
.I errno
should be set appropriately.
.B ldap_initialize()
and
.B ldap_init_fd()
will directly return the LDAP code associated to the error (or
.I LDAP_SUCCESS
in case of success);
.I errno
should be set as well whenever appropriate.
.B ldap_set_urllist_proc()
returns LDAP_OPT_ERROR on error, and LDAP_OPT_SUCCESS on success.
.SH SEE ALSO
.BR ldap (3),
.BR ldap_bind (3),
.BR ldap_get_option (3),
.BR ldap_set_option (3),
.BR lber-sockbuf (3),
.BR errno (3)
.SH ACKNOWLEDGEMENTS
.so ../Project
